Direct-current amplifier and circuit



April 5, 1949. H. H. WEICHARDT 2,466,065

DIRECT CURRENT AMPLIFIER AND CIRCUIT Filed Sept. 8, 1944 g 4 I/ '0 2 g kF I I4 I I is L I I8 Oor+ a J V V L O Oor- W 1 +V+X +V F I G 2 INVENTOR.m-zmz HERMANN WELGHARDT J 1: BY Y Patented Apr. 5, 1949 U NiITI-JETDPATENT OFFICE v DIRECT-CURRENT AMPLIFIER AND CIRCUITHeinzrHerma'nmWeicliardt, New York, N. Y.,, as-

:signorto: Tung-Sol Lamp- Works, Inc., Newark,

N.- .L, a corporation of Delaware Application-September 8, 1944, SerialNo. 553,178

-1-6:Claims-.. (Cl. 315-15) invention relates to amplifier tubes andmore. particularly to low voltage Dl C. amplifier tubes and circuitstherefor; I

An object of the invention is-toprovidean amplifier of this type that'will be small, about the size of the conventional receivingtube, andwill have a high amplificatiom factor;

Anotheriobiect ofthe invention is i to provide connected foramplification otvoltage variations:

of aphotocell. 7

Mynew amplifier i'sshown-at 2-0.

In Fig. 1, lrepresents diagrammatically any suitable evacuated envelope'forthe elements of" the new amplifier; which elements include acathode-2', preferably o'fthe indirectly heated type, an electronic lens Icomprising slot'te'd' 'electrodes 4-" and" 6 and a meshelectrode 'B'positioned therebetween, a control electrodel ng atarg'et' l2, asuppressor grid 1 "4 and an electrode I B' -adaptedto: be maintained 'atthe potential of the electrode:

6. as by the connection l 8 therebetweem In use; mesh electrode ismaintainedlatz-a potential substantially higher than that :"of'electrade6. Thus if electrodest' and [6 are at potential V; electrode 8 will} beat: a pot'entialz of- V ta The potential 'of electrode: 4 may be equalto that of "th'e" cathode, or' it may be negative with respect thereto.The three where a: is positive;

electrodes together form: an electronic lens, the.

equi-potential 'iines'of which: :are: indicated in. the drawing. 'Byformingthe-electrode: 8 ot'wire' mesh, the diverging effect of'anintermediately positioned slotted l'en's' "of" high potential.- ;is

avoided. The optical equival'ent'o'f. the threeielec trodeelectroniclens: is theiv two simple converging lenses symb'olically indicatedfiatilnrarrd:Lz in -the: drawing; The current 'absorbedkiby electrode'=:8=

wire'di'ameter to'=me'sh opening. :m'one' hundred.

mesh of .002" wire serves satisfactorily for the electrode 8. Whenthe'potential of electrode'8 is about one and one-half: times thatofelectrode 6 the' electron beamma-y-be brought to a focus at ajpointabout 15mm. from the:=-lens.. Due

tothe relatively low potentials employed say from'200: to 500.'volts' onelectrode 8, the'velocity of: the electrons leaving. the lensislet/enough. for deflection by the control electrode 10 duringv theshort distance of travel of the beam-toward. the target I2.

As shownin. Fig. 1',, electrodes. l0- and. iii are elongatedlongitudinally ofthe tube-so. as to influence the electronbeamthroughout its path.

Electrode l=0- preferably flares" outwardlytominimize the drawing ofcurrent by that electrode;

Target I2: is preferably maintained at the quiescentpotentialofelectrodeit), which sub-1 stantially'that ofelectrodes l6 and 6'. The suppresscr4 is T maintained: at the cathode potential Its: function is toprevent-the flow of secondary or slightly positive with respect thereto.

electrons from thetarget from reaching electrode l6 and. to shield-thetarget from electrode 5,

thereby preventing'the potentialdifference, set.

up during operation of the tube, from. reacting on the. deflection ofthe beam;-

During operation of the tubethe: positive voltages, the'variations ofwhich are tobe amplified, are applied to electrode [0.

I0 is substantially equal to that of electrode Hi,

there is no. deflection of the beam of electrons and hence but arelatively small part of the beam falls on the target 12. Upon anincrease ofpotential of electrode-ldthe beam is deflectedto. increasethe flow of electrons to the target.

Consequently the targetpotential decreases in proportionv to theincrease of potential on electrode l0. Upon decrease inpotential onelectrode Hkthe beam is deflected toward electrode l 6withccnsequentreduction in target-current and corresponding: increase ofpotential: thereof. The potential swing, of the target is substantially.

greater'lthan that of. the control electrode- -lll.

and hence the tube. operates as an. amplifier. With a tube of thesize-of a-conventional-receiving tube an-amplification factor of IL=100'can be? easily obtained. The beam currentinzsuch At the quiescent.potential, that is, when the potential of electrode:

tube when the potential of electrode 6 is about two-thirds of electrode8 is about 1 milliampere.

In Fig. 2 the new amplifier, indicated at 20, is shown with its controlelectrode [0, connected directly to the anode of a conventionalthreeelectrode amplifier 2|. Amplifier 2|, in the particular circuitillustrated in Fig. 2, is connected to amplify voltage variations of aphotocell 22. A voltage divider 24 across the ends of which a constantpotential difference of a few hundred volts is maintained, has a tap 26,near the positiveend, connected directly to the positive electrode ofthephoto cell 22 and connected through a resistor 28 to the anode ofamplifier 2|. The positive end of divider 24 is connected directly toelectrode 8 of the lens of tube 20 andthrough a resistor 30 with thetarget l2. El'eca trodes l6 and 6 are connected through a lead 32 withan intermediate poin't'on divider 24. The

and electrode 4 of the lens in the specific embodiment of the inventionillustrated is connected to the negative end of the divider. The controlgrid of amplifier 2| and thenegative electrode of the photo-cell areconnected through a resistor 34 with a point on the divider of potentialnegative with respect to the cathodes.

The operation will be clear from the above description. Variations ofvoltage of the photocell 22 applied to the grid of amplifier 2| willappear as amplified variations in the positive potential of the anode ofthat tube. The varying positive potential of control electrode [0, beingthat of the anode of amplifier 2 I, will cause corresponding deflectionsof the beam of electrons issuing from the electronic lens withcorrespondin amplified voltage variations appearing on target I2. Henceamplified voltages will appear across terminals 35 and 36, connected,respectively, with the cathodes of the tubes and with the target. Theseamplified voltagescould be applied directly across the control electrodeand cathode of a succeeding tube if further amplification is desired.

The amplifier requires but relatively low operating voltages and thepositive potentials, the var iations of which are to be amplified, canbe applied directly to the control electrode or "grid without suchelectrode drawing substantial current. The small size of the amplifieris made possible by the provision of the electronic lens having onlyconverging elements to which relatively low operating potentials areapplied; the lens converging the electron stream from the cathode into abeam of short focal length with the electrons thereof moving relativelyslowly so as to be readily influenced by changes in the controlpotential.

The new amplifier tube and circuit have now been described withreference to the drawings. It will be understood that various changes inthe circuit or tube elements diagrammatically shown in the drawing couldbe made without departing from the spirit of the invention. For example,the electrode 8 of the electronic lens has been diagrammaticallyillustrated as being throughout of wire mesh. As the part of thiselectrode alined with the slots in electrodes 4 and 6 is the only partthrough which the electrons penetrate, it is not necessary that theentire electrode be of mesh. In practice the electrode 8 could, andpreferably would, be made of a slotted metal sheet with wire meshcovering the slot.

The following is claimed: I

1. The low voltage direct current amplifier comprising a source ofelectrons, an electronic lens adapted to form the electrons from saidsource into a converging beam of short focus, a target adjacent thefocal point of said beam and a control electrode positioned to deflectsaid beam upon changes of positive potential and flared outwardlytherefrom.

2. In a low voltage direct current amplifier having a cathode, a controlelectrode and an anode target, a three-electrode electronic lenspositioned between said cathode and said control electrode, said lensforming the electrons emitted by said cathode, into 'a converging beamof short focus.

3. The combination in'an amplifier tube of a cathode, control electrode,anode target and convergent electronic lens, said lens being positionedin the path of electrons emitted by the cathode andoperating to form aconvergent beam of short focus and said control electrode beingpositioned 4. A low voltage direct current amplifier having a controlelectrode adapted to operate at positive potentials comprising incombination an evacuated envelope, a cathode, a 3-element convergentelectronic lens, a, target and a diverging control electrode all withinsaidenvelope, said control electrode being positioned between said lensand said target and to one side of the convergent electron beam formedby the lens andsaid lens being so formedthat the optical equivalentthereof is a pair of simple convergent lenses.

5. An amplifier comprising in combination a cathode for emission ofelectrons, a slottedfirst electrode adjacent to said cathode andmaintained at a potential not greater than that of the oathode, a secondelectrode maintained at a potential substantially Positive with respecttothe cathode, at least that part of said second electrode alined withthe slot of said first electrode being of mesh, a slotted thirdelectrode maintained at apotential positive with respect to the cathodeand lower than that of said second electrode, said three cathode foremission of electrons, a slotted first electrode adjacent to saidcathode and maintained at a potential not greater than that of thecathode, a second electrode maintained at a potential substantiallypositive with respect to the cathode, at least that part of said secondelectrode alined with the slot of i said first electrode being of mesh,a slotted third electrode maintained at a potential positive withrespect to the cathode and lower than that of said second electrode,said three electrodes together comprising an electronic lens for formingthe electrons emitted by said cathode into a convergent beam of shortfocus, a target positioned adjacent the focal point of. the electronbeamand a con mete and an electrode positioned betweenthe lens and thetarget and:fonzitheppposite side of the beam fromsaid control electrode,said last mentioned electrode .being maintained'atfthe potenti'allofsaid third 'electrode". 7 p

7.? l amplifier "comprising ,i'in'." combination: a cathode. ;foremission 'ofel'ectrons; a slottedfirst electrode adjacent" to said"cathode and 'Tmain'; tainedilat a: potential .not'greate'r than? that:of theicathode';- a "second electrode "maintained fiat a potential"substantially"positive :With respect to the I cathodefatdeast that"part of said :se'cond electrode alined with the "slot of saidfirst-elec' trode *being-.:"of *m'esh'; aslottedthird electrodemaintained'at a potential positive with"respect to the cathode .andlower'ithan' that of said second electrode, said three electrodestogether come prising an electronic lens forfforming theJelectronsemitted "by 'said'cathode into a convergent beam ofshort'ffocus-,1;a.target positioned adjacent the focal pointiofvtheelectron beam.and a control 'ele'ctr'ode positioned "between' thelens and the target and to one side of the electron beam" for deflectionthereof toward and from the target and an electrode disposed on theopposite side of the beam from the control electrode and maintained atthe potential of said third electrode and a suppressor maintained atsubstantially the cathode potential and positioned adjacent the targetfor shielding the target and suppressing the flow of secondary electronstherefrom.

8. An amplifier comprising in combination a cathode for emission ofelectrons, a slotted first electrode adjacent to said cathode andmaintained at a potential not greater than that of the cathode, a secondelectrode maintained at a potential substantially positive with respectto the cathode, at least that part of said second electrode alined withthe slot of said first electrode being of mesh, a slotted thirdelectrode maintained at a potential positive with respect to the cathodeand lower than that of said second electrode, said three electrodestogether comprising an electronic lens for forming the electrons emittedby said cathode into a convergent beam of short focus, a targetpositioned adjacent the focal point of the electron beam and a controlelectrode positioned between the lens and the target and to one side ofthe electron beam for deflection thereof toward and from the target saidcontrol electrode being operated at potentials positive with respect tothe cathode and being flared outwardly from the beam to minimiz thedrawing of current.

9. An amplifying circuit, comprising two amplifier tubes, one of saidtubes being a conventional tube having a control grid, an anode and acathode and the other of said tubes being a low voltage direct currentamplifier having a cathode, an electronic lens for forming electronsinto a converging beam, a target and a control electrode positioned todeflect the beam formed by the lens, a connection between the cathodesof said tubes, a connection between the anode of said first tube and thecontrol electrode of said second tube, and means for maintaining saidanode and said target at potentials positive with respect to the oath--odes whereby variations in potential applied to the control grid of thefirst tube appear at the anode thereof and at the control electrode ofthe second tube as amplified variations in positive po- 6*tennsranarappeae further amplifiefd at-ithe'targetii of said secondtube-2;;

10. An amplifying circuit, comprising-ktwo am plifier tubes, one of saidtubesi'beingqai convene-1 e tional tube having "a icontrolagrid;'antanode and 2 a cathode and the other of said 'tubeszbeing a low"voltage di'rect current amplifier rh'aving 'a caths odegsan electroniclens forlformingtelectrons :into 3 I I a converging abe'am; a ltargetand fa lcontrolriele'c- 1dttrode positionedwto deflect lthebeamfo'rmed:by theile'ns, a connection *betweenifhe cathodes (of? said -tubes; aconnectionilbetween the *anodecoff said first tube :and .the controlelectrodeieoffisaidcl second tube, and means for maintaining said-"an;mi; odean'd'said target at potentials-positive withxrespe'ctto thecathodes whereby variations-infpoten tia'li applied to' the contr'oli'gridxiof :tlie .zfirst 'tube appear atwthefianode thereof ianclatrtheicontrol electrode -ofthe second ?tube: as. amplifiediivariae203;; tion so in positive'apotentialz i and:- appear 1 furtheramplifiedl, atithe target "of said :fsecond tube; said; electronic lenscomprising convergent '1 elements 1 only? 1 1. Am amplifying circuitcomprising 1 two tame. plifien :tubs, one of 'said tubes: beingacconviene tional-:tube having a control' 'grii anr'anode-and: acathode' and 'the.-: other :of said ttubes beingsta-a low voltage directcurrent amplifier having a oath ode; an electronic lens forcformingelectrons-1 into a converging 'zbea-msatar-get antla 's-controli :elecetlOdz'DOSi-tiblled 217C)? defie'ct 'the vbeam formed by the lens, aconnection between the cathodes of said tubes, a connection between theanode of said first tube and the control electrode of said second tube,and means for maintaining said anode and said target at potentialspositive with respect to the cathodes whereby variations in potentialapplied to the control grid of the first tube appear at the anodethereof and at the control electrode of the second tube as amplifiedvariations in positive potential and appear further amplified at thetarget of said second tube, said means for maintaining the potentials ofsaid anode and target positive with respect to said cathodes comprisinga voltage divider having a connection adjacent its negative end to saidcathodes, a resistor connected between said anode and a point adjacentthe positive end of said divider, and a resistor connected between saidtarget and the positive end of said divider and wherein said electroniclens comprises a first slotted electrode connected to the negative endof said divider, a second mesh electrode connected to the positive endof said divider and a third slotted electrode connected to anintermediate point on said divider.

12. A direct current amplifier comprising a cathode, a controlelectrode, a three element electronic lens for converging the electronbeam from said cathode and a target anode all within an evacuatedenvelope substantially the size of a conventional receiving tube.

13. A direct current amplifier comprising a source of electrons, a threeelement electronic lens for forming the electrons from said source intoa convergent beam said lens having a center element formed at least inpart of wir mesh, a target adjacent the focal point of said beam and acontrol electrode positioned to deflect said beam upon changes ofpotential.

14. A direct current amplifier comprising a source of electrons, anelectron lens adapted when potentials of the order of a few hundredvolts are applied thereto to form the electrons from said source into aconverging beam having a focal 7, length of the order of 15 mm., atarget adjacent the focal point of said beam and a control electrodepositioned to deflect said beam upon changes of positive potential.

15. An amplifier tube comprising a source of electrons, a three elementelectron lens converging the beam of electrons upon the application of arelatively low voltage thereto, a target adjacent the focal point ofsaid converging beam, a control electrode positioned between the anodeand the lens to deflect said beam upon changes of positive potentialapplied thereto, and a suppressor grid positioned between the controlelectrode and the anode.

16. An amplifier tube comprising a cathode for the generation of anelectron beam, an electronic lens adjacent said cathode having at leastthree elements, the outer elements having slots therein and the middleelement being formed of a wire mesh, said lens operating to converge theelecg0 REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS Number Name Date 2,075,142 Schlesinger Mar, 30,1937 2,165,308 Skellett July 11, 1939 2,219,117 Schade Oct. 22, 19402,227,016 Schlesinger Dec. 31, 1940 2,255,485 Dome Sept. 9, 19412,265,311 Preisach et al. -1 Dec. 9, 1941 2,299,047 Winans Oct. 13, 19422,303,166 Laico Nov. 24, 1942 2,351,501 Gray June 13, 1944 2,358,902Ziebolz Sept, 26, 1944 2,372,328 Labin Mar. 27, 1945 FOREIGN PATENTSNumber Country Date 623,769 Germany Jan. 3, 1936 OTHER REFERENCES Myers,Electron Optics, Nostrand 00., N. Y. city, 1939, page 472.

